This invention relates to a NIR spectroscopy method for analysis of chemical process components, e.g. for analysis of bitumen and solvent-diluted bitumen from froth treatment during oil sands processing.
In analytical or research activities, as well as in industrial chemical processes, there is a need for highly reliable real or near real time analysis of chemical components, e.g. for froth treatment during oil sands processing. In the extraction of bitumen from oil sands, froth treatment is an essential step for removing water and solids from bitumen froth to produce bitumen meeting product specifications. The bitumen froth usually contains about 60 wt % bitumen, 30 wt % water, and 10 wt % solids. Current commercial froth treatment employs naphtha dilution followed by multistage centrifugation, which gives a diluted bitumen product typically containing about 0.3 to 1.0 wt % solids and about 1 to 5 wt % water. An alternative froth treatment process uses aliphatic solvent as froth diluent. A diluted bitumen product that contains less than 0.1 wt % water and solids and controlled levels of asphaltenes can be produced. It has previously been shown that, the performance of the froth treatment process using aliphatic solvent depends greatly on controlling process parameters; among the most important of these are the solvent-to-bitumen ratio (S/B, by wt), asphaltenes rejection level, and density of the solvent-diluted bitumen oil phase. Successful control of these process parameters ensures the desired level of asphaltenes in product, sufficient settling flux of water and solids, and on-spec product (e.g., containing less than 0.1 wt % water plus solids).
At present, the S/B of solvent-diluted bitumen is determined by vacuum rotary evaporation (Rotavapor), the asphaltenes content of bitumen is analyzed using the standard ASTM or IP methods that are based on precipitation of asphaltenes by light aliphatic solvent and followed filtration, and the density of solvent-diluted bitumen is measured using a laboratory density meter. These analyses are labor-intensive and time-consuming. Rotavapor takes approximately 1.5 h to complete and asphaltenes content analysis takes about 6 h. Furthermore, the accuracy of the analytical results depends on the skill of the analyst. Consistency of the results from various laboratories is frequently not satisfactory. Therefore, more reliable and faster analytical methods are required to better monitor performance and to permit timely adjustments of the operating conditions of the froth treatment process.
Near-infrared spectroscopy (NIR) provides information on chemical and physical properties of sample components. Chemometric methods based on eigenvalue decomposition of a data matrix are effective tools for analyzing correlations between spectral information and compositions and properties. Principal component analysis (PCA) and partial least squares in latent variables (PLS) are commonly used techniques. NIR in combination with chemometrics is hence a powerful approach for fast routine and on-line chemical analyses.
U.S. Pat. No. 5,742,064, issued Apr. 21, 1998, describes a system for detecting water and dirt in petroleum flowing through a pipeline. Light is projected into the petroleum and light which is not absorbed by impurities contained in the petroleum is transmitted to a photomultiplier or spectrometer. Three different optical waveguides are used and the light source is a tunable laser.
A method for measuring asphaltene concentration of hydrocarbon feedstocks using spectroscopy is described in U.S. Pat. No. 6,087,662, issued Jul. 11, 2000. IR spectroscopy is used in mid-range IR frequencies between about 3800 cm−1 and 650 cm−1. This uses an ATR and a photomultiplier. It has an absolute accuracy of about 0.9–1.3% for asphaltenes contents below 4%.
Heint et al., U.S. Pat. No. 6,300,633, issued Oct. 9, 2001, describes an in-line spectrometric method for determining the residue content of an isocyanate. It uses a probe capable of directing light at wavelengths of from 1050 to 2150 nm into a process stream. A near-infrared spectrum is generated and the residue content is determined using a chemometric model.
It is an object of the present invention to provide a method for using NIR spectroscopy for analysis of bitumen and solvent-diluted bitumen samples from the bitumen froth treatment process, that can be used for fast routine and on-line analysis.